Japanese Examined Patent Publication No. 71090/1992 discloses a cationic electrodeposition coating composition prepared by reacting an epoxy-containing acrylic polymer, a bisphenol compound and a bisphenol diglycidyl ether-type epoxy resin to produce an epoxy-containing resin, introducing thereinto cationic groups and adding a blocked polyisocyanate compound.
The above electrodeposition coating composition, however, is insufficient in curability and in corrosion resistance of the cured coating film. To improve these properties, a lead compound such as lead acetate, lead 2-ethyl hexanoate or lead silicate is generally added.
The lead compound, however, is toxic and causes environmental pollution. Therefore, a need exists for a lead compound-free cationic electrodeposition coating composition which is excellent in curability and in corrosion resistance of the cured coating film.